The number of digits in the product of the 39 successive primes produced by the formula n2 + n + 41, where n = 1 to 39. This formula was used by Charles Babbage to demonstrate the capabilities of his Difference Engine (1819-1822). [Haga]

Combine two digits of a number in order (from right to left) alternating them with + then -. If the result is 0 or a multiple of 101, the prime number 101 divides it.
E.g., Is 575519513 divisible by 101? 13 - 95 + 51 - 75 + 05 = -101. Yes! [Luhn]

The Math Forum was one of PC Magazine's Top 101 Most Incredibly Useful Web sites in the Information category for the year 2003.

Room 101 is the name of a British TV series in which celebrities are invited to discuss their (often whimsical) pet hates with the host.

In a short section titled "Prime Numbers ... and Monkeys" of Danica McKellar's bestselling book Math Doesn't Suck, the following statement can be found: "It's hard to believe that there's no way to evenly divide up 101, but it's true!"

Christopher Hornsrud, Prime Minister of Norway in 1928, is believed to be the longest lived Prime Minister of any country. He died at age 101. [Duffy]

A radio astronomer in the movie Contact makes the statement "OK, a hundred and one, the pulse sequence through every prime number between two and a hundred and one." [Haas]

Aging 101 is a series of general information articles on aging that school teachers and their students can use in a variety of courses. Its intent is to have you make it until at least 101 years of age.

101^101-100^100+99^99-98^98+...-2^2+1^1 is prime.
Note that 101 is the only known odd prime p, such that
p^p-(p-1)^(p-1)+...-2^2+1^1 is prime. [Firoozbakht]

101 is the first three-digit prime number that
can be both read backward and upside-down without being
changed. [Mosse]

The sum of 10 first primes plus 1. Note that 101 is 10 and 1 concatenated. [Abramson]

A googol (10^100) contains 101 digits. The search engine Google's play on the term reflects the company's mission to organize the immense amount of information available on the web.

"The 101 Car" is used as the Regional Tourist Information Center in Big Stone Gap, Virginia.

The smallest prime which requires a multidigit prime number
of digits (base 10) and a prime number of chisel strokes as
a sans serif Roman numeral. Curiously, this is true whether
one considers "C" to be one stroke (a circular arc) or two
strokes (like a left angle-bracket or less-than sign). [Post]

The first five consecutive powers of 101 produce
palindromes. The next 4 consecutive powers of 101
produce 'quasi-palindromes' in the sense of
concatenating several multidigit numbers in reverse
order, but not reversing the digits of those individual
numbers. In all these powers the numbers in the rows
of Pascal's Triangle can be seen in order (with somezeros thrown in here and there so that each number,
after the first, occupies a two-digit space), hence the
name 'Pa-sca-lindromes'.

In the classic fairy tale Sleeping Beauty, the lovely princess was awakened back to life by a smitten prince's kiss laid on the 101th year following her accidentally prick-induced trance, in accordance with the
attenuated curse. [Beedassy]

The palindromic ZIP Code of Brimfield MA is 101 with a zero on each end.

The only 3-digit number whose digits are neither prime nor
composite. [Gudipati]